This invention relates to shaft couplings, and more particularly, to disc pack couplings for transmitting torque between two shafts approximately aligned on a shaft axis.
Flexible disc pack couplings, such as Thomas Flexible Disc Couplings sold by Rexnord Industries, Inc., Milwaukee, Wis., are known in the art for transmitting torque between adjacent generally axially aligned first and second shafts. These couplings include a disc pack interposed between a pair of hubs or formed part of hub assemblies including end adapters.
Each disc pack is typically formed from a plurality of stacked coaxial discs and either surrounds the hub outer cylindrical diameter directly adjacent to the coupling far end or is captured inside of specially machined additional components. This arrangement inhibits the ability of the hub to accept large shaft bore diameters and requires the use of low profile headed specialty fasteners and/or results in the necessity of providing more costly end adapters.
Alternatively, each disc pack is captured between large radially extending flanges forming part of the hub and end adapter. Each flange includes holes for a bolts which connect the flanges to the disc pack. The bolts connect the hub and end adapter in an alternating arrangement to the disc pack. This arrangement requires large diameter separate flanges to accommodate the bolt hole arrangement which mandates expensive components. Sandwiching the disc packs between the end adapter and hub hides the disc pack from view and requires disassembling the coupling to inspect the disc packs for wear. Moreover, upon the failure of both of the above described types of couplings, upon failure of the disc pack, the shafts can rotate uncontrollably causing damage to the rotating equipment connected to the shafts.
Nested disc pack couplings are especially suitable for use in applications where shaft coupling must be maintained upon failure of the disc pack. This is accomplished by providing hub assemblies including a hub having a non-circular perimeter loosely nested in a non-circular cavity formed in an end adapter fixed to the shaft end. The disc pack resiliently couples the hub to the end adapter. The hub assemblies of the coupling are joined by a center member that transmits torque between the hub assemblies. Upon failure of the disc pack, the hub engages the end adapter to allow an orderly shut down of the rotating shaft.
Unfortunately, in known nested couplings, inspection of the disc pack is difficult because the disc pack is shielded from view. As a result, the coupling must be disassembled to properly inspect the coupling. This is time consuming and expensive. Moreover in known nested couplings, the flexing disc pack can be physically restricted by physically contacting the hub or end adapter. Therefore, a need exist for an improved disc pack coupling.